Tocopherol compounds, also designated as Vitamin E, are the active components of certain vegetable oils. Vitamin E activity refers to the physiological activity of this group of nutrient materials. Materials having Vitamin E activity all belong to a distinct series of compounds which are all derivatives of chroman-6-ol. These compounds are all tocol derivatives having an isoprenoid C.sub.16 side-chain, including those compounds having an unsaturated C.sub.16 side chain. The term "tocol" is used to mean 2-methyl-2-(4',8',12'-trimethyltridecyl) chroman-6-ol. Alpha-, beta-, gamma- and delta-tocopherols are of primary importance for Vitamin E activity, and are commercially isolated from various natural sources. Also important are the enols such as tocodienols and tocotrienols which are tocopherol compounds having an unsaturated side chain. Within this description the terms "tocopherols" and "tocopherol compounds" are understood to include such unsaturated toco-enol compounds.
Tocopherols, found widely distributed in organic substances, occur in highest concentrations in cereal grain oils, principally in wheat and corn oils, and also in barley and rye. They are also found in vegetable oils such as safflower, soybean, peanut, cottonseed, linseed, sunflower, rapeseed, palm, and in other vegetable sources.
In general, tocopherols are widely used for their antioxidant and Vitamin E activity. They are of great value in foods, feeds and medicines for these reasons. Frequently, mixtures of tocopherols are isolated, purified, and methylated to upgrade Vitamin E activity.
Those tocopherol compounds having an unsaturated C.sub.16 side-chain such as tocotrienol can be hydrogenated and then the beta, gamma, and delta isomers can be upgraded to alpha-tocopherol vitamin E activity.
Natural vegetable oils contain small amounts of tocopherols. Such oils as wheat germ oil, soybean oil, and cottonseed oil are considered to be the best sources of Vitamin E. It is desirable for commercial purposes to separate and concentrate tocopherol-containing materials and to devise methods for separating impurities from tocopherols so that they may be employed for their anti-oxidant and Vitamin E activity. A variety of methods have been developed which accomplish this. One such method is reported in U.S. Pat. No. 3,122,565 which involves mixing tocopherol-containing material with a polar organic solvent and contacting this mixture with a strongly basic anionic exchange resin whereby tocopherols are adsorbed on the resin. The tocopherols can then be eluted by passing an acidic eluding solution through the resin. Difficulties such as fouling frequently develop with resin systems. Resins furthermore have a low capacity, are shortlived and expensive. It would therefore be advantageous to develop methods for isolating and purifying tocopherol compounds which may be done continuously and without the use of resins. A method is described herein whereby tocopherols may be effectively extracted and purified in a liquid extraction system. When, in accordance with the instant invention, caustic methanol is used to extract and purify tocopherols, impurities such as squalene, dehydrated sterols, and waxes are separated and removed from the tocopherol.